1. Field of the Invention
The present invention relates to a color space scalable video coding and decoding method and an apparatus for the same, and more particularly, to a color space scalable video coding and decoding method and an apparatus for the same that can adjust color components or color depth according to the performance of a decoder side.
2. Description of the Prior Art
With the development of information and communication technologies, multimedia communications are increasing in addition to text and voice communications. The existing text-centered communication systems are insufficient to satisfy consumers' diverse desires, and thus multimedia services that can accommodate diverse forms of information such as text, images, music, and others, are increasing. Since multimedia data is large, mass storage media and wide bandwidths are required for storing and transmitting multimedia data. Accordingly, compression coding techniques are required to transmit multimedia data, which includes text, images and audio data.
The basic principle of data compression is to remove data redundancy. Data can be compressed by removing spatial redundancy such as the repetition of the same color or object in images, temporal redundancy such as little change in adjacent frames of a moving image or the continuous repetition of sounds in audio, and visual/perceptual redundancy, which considers human insensitivity to high frequencies. In a general video coding method, temporal redundancy is removed by temporal filtering based on motion compensation, and spatial redundancy is removed by a spatial transform.
In order to transmit multimedia after the redundancy has been removed, transmission media are required, the performances of which differ. Presently used transmission media have diverse transmission speeds. For example, an ultrahigh-speed communication network can transmit several tens of megabits of data per second and a mobile communication network has a transmission speed of 384 kilobits per second. In order to support the transmission media in such a transmission environment and to transmit multimedia with a transmission rate suitable for the transmission environment, a scalable video coding method is most suitable.
This scalable coding method makes it possible to adjust the resolution, the frame rate, the signal-to-noise ratio (SNR), and others of a video by truncating part of a pre-compressed bit stream in accordance with environmental conditions such as the transmission bit rate, the transmission error rate and system resources. With respect to such scalable video coding, MPEG-21 (Moving Picture Experts Group-21) Part-13 has already progressed its standardization work.
However, since the existing scalable video coding cannot provide scalability in a color space, even a display device that requires a grayscale image instead of a color image must receive and decode the color image, which is unnecessary and inefficient. Further, it is inefficient for a display device that is unable to display an image having a color depth of 24 bits to receive and decode a bit stream coded with a color depth of 24 bits and then truncate unnecessary bits from the decoded bit stream.